Heron’s Odometer

The so-called Heron’s odometer was most probably an invention made by Archimedes. Vitruvius was the first writer who mentioned the instrument(1st cent. BC). Its full description is found in Heron’s work Dioptra or On Dioptra. The odometer was used in order to calculate road distances, while a later variation known as nautical odometer was used to measure distances at sea. The function of the mechanism relies on a system of cogwheels (gears) which, assembled in atermones kochlies, transferred the movement of the wheels onto three circular discs at the upper part of the instrument, where the travelled distance was measured.